The New Yorker:
In 1992, Martin Chalfie made a spectacularly useful discovery, which I like to think of as perhaps the greatest use of cut-and-paste. Chalfie began with the fact that every gene has two parts: an encoding sequence that, using RNA as an intermediate, specifies a set of amino acids from which a cell can synthesize a protein, and a regulatory sequence that specifies, indirectly, when and where that protein should be built.
The impact of this on understanding neuroscience is immense. As Steven Pinker once put it (at the prompting of Stephen Colbert), the secret to the brain is that “brain cells fire in patterns.” But the trick to understanding the brain is to understand which cells fire in which patterns—when and where.